Thousand Island is a pure Elixir, OTP-based socket server library inspired by Ranch. It provides a supervision tree (Server → Listener + AcceptorPoolSupervisor → AcceptorSupervisor → Acceptor/DynamicSupervisor → Handler) that handles TCP and SSL connections with configurable concurrency, connection draining, and shutdown semantics. The library exposes a clean `ThousandIsland.Handler` behaviour for application-level protocol logic, and a `ThousandIsland.Socket` abstraction that decorates underlying transport sockets with automatic telemetry instrumentation. It emits rich telemetry spans for listeners, acceptors, and individual connections, supports suspend/resume of connection acceptance, and handles transient network errors and file descriptor exhaustion without crashing the acceptor tree. The code is thoroughly tested and free of external dependencies beyond telemetry, making it both a production-ready server and an exemplar of idiomatic Elixir/OTP patterns.